A gas mask and breathing equipment of the type has become known from  GB 2 058 577 A. A safety helmet with a transparent visor is located at the head of a user of the device. A blower draws in ambient air via a filter and delivers it via an air channel, which extends on the inner side of the safety helmet from the nape area to the face. The breathing air then flows on the inner side of the visor in the direction of the eye area to the area of the mouth and enters the environment via an expiration valve on the underside of the visor. The visor is in contact with the face of the user of the device via a sealing lip, so that a chamber that is sealed toward the ambient atmosphere is formed between the face of the user of the device and the inner side of the visor. The breathing effort of the user of the device is measured with a pressure sensor arranged inside the chamber, and the gas flow is throttled during the phase of expiration.
The drawback of the prior-art gas mask and breathing equipment is that a comparatively high breathing gas flow is needed during the phase of expiration in order to flush the expired carbon dioxide out of the chamber. The electric power needed to drive the blower, which is supplied by a battery or a battery pack in portable devices, has an adverse effect on the operating time of the gas mask and breathing equipment, so that the user of the device must leave the site of the mission prematurely.